The Effect of Tool Design on the Friction Stir Welding of Thick Aluminum Alloy AA6082-T651 Extruded Flats

Abstract

Fifteen-millimeter-thick aluminum alloy AA6082-T651 extruded flats were friction-stir-welded by using three different types of tool pin profiles, i.e., (1) conical with only left-hand threads (CL), (2) conical with both left-hand and right-hand threads (CLR), and (3) conical cam-tri-flute with left-hand threads (CTFL) up to a height of 6 mm from the pin tip. The microstructures and the mechanical properties across the weld thickness were characterized. Tunneling defect was found at the weld-bottom for the CL tool pin profile and at the weld-top for the CLR pin profile. The reasons behind the formation of such defects have been analyzed and discussed. On the other hand, a defect-free joint was obtained with the CTFL pin profile. Tensile test samples were machined from top, middle, and bottom sections of the welds, and tensile strengths were measured for all the sections to determine the joint efficiencies. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were employed to identify and study the morphology of the coarse phase particles present in the base material and in different regions of the welds. These results were correlated with the microhardness contours plotted across the weld cross section.

The Influence of Tool Pin Geometry and Speed on the Mechanical Properties of the Bobbin Tool Friction Stir Processed AA1050

“…The low surface roughness attains at the travel speed of 500 mm/min and the rotation speed of 1400 rpm. Figures [13][14][15] show the macrostructures of the AA1050 BT-FSPed at travel speeds of 50, 100, 200, and 300 mm/min and a constant rotation speed of 600 rpm using three-pin geometries of Tr, Sq, and Cy, respectively. The typical regions of SZ, thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ), and BM can be observed at all the applied processing parameters.…”

“…In recent years, FSP technology using a conventional tool (CT) design has been widely applied to aluminum and its alloys only to modify the microstructure of the material surface with and without ceramic particles additions [10,11]. For AA1050 alloy, many researchers have paid attention to utilizing the FSP technique with a CT design for welding [12][13][14] and processing [15][16][17] based on different parameters. Bobbin tool (BT) design is an innovative tool design and was initially used in the FSW of aluminum alloys [18][19][20][21].…”

Friction Stir Welding of Thick Plates of 4Y3Gd Mg Alloy: An Investigation of Microstructure and Mechanical Properties

“…The solidstate friction stir welds have showed an efficiency of the order of 90% [12]. Lately, FSW of thick sections has also been explored by researchers [13][14][15][16]. For AA7075 aluminum alloy, Rao et al [13] attained a joint efficiency of 70% and 53% for 10 mm and 16 mm plate thickness, respectively.…”

“…Comparisons between FSW and underwater FSW for 19 mm thick AA2519 alloy have also been performed [14]. Further, the impact of tool design and process parameters for thick section FSW of aluminum alloys has also been addressed [15,16]. Due to increase in plate thickness, thermal disparity across the weld depth is found to influence mechanical and microstructural features in AA2219 alloys [17].…”